Synthesis gas mainly containing hydrogen (H2) and carbon monoxide (CO) is widely used as a raw material for liquid fuel oils such as Gas-to-Liquids (GTL) and dimethyl ether (DME) and chemical products such as ammonia, methanol, and acetic acid. As a raw material for synthesis gas, a light hydrocarbon gas such as natural gas can be used. Synthesis gas having a H2/CO molar ratio of about 0.5 to 3 can be efficiently produced by adding steam or carbon dioxide to such a raw material gas in the presence of a catalyst and supplying heat required for reaction.
For example, when the raw material gas is methane, by adding steam, synthesis gas having a H2/CO molar ratio of 3 can be produced by steam reforming reaction represented by the following formula 1. On the other hand, when carbon dioxide (CO2) is added, synthesis gas having a H2/CO molar ratio of 1 can be produced by CO2 reforming reaction represented by the following formula 2.CH4+H2O═CO+3H2  [Formula 1]CH4+CO2═2CO+2H2  [Formula 2]
Both reforming reactions represented by the formulas 1 and 2 are endothermic. Therefore, in addition to an auto thermal reforming (ATR) reactor and a partial oxidation (POX) reformer, a tubular-type reformer, in which catalyst tubes provided in a heating furnace are heated by radiant heat from combustion gas, is conventionally used as a reactor (reformer) (Patent Literature 1). Particularly, many synthesis gas plants use tubular-type reformers because synthesis gas can be efficiently produced oven when the amount of synthesis gas produced is relatively small.